OPT: msct_pca: modes visualization
OPT: msct_pca: modes visualization

Former-commit-id: b3969f5113332eb3b46cd5538581cc73d7bea8fc [formerly 82ace373179fc925da707f90c8b6b999049d9705]
Former-commit-id: 53bed0cd384a189f166248c335044fe72bd281ff
Former-commit-id: 91de31d9d3aa407400bf8e3684b3fc82ed368b8f
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox